PD-60332
IR3821AMPbF
SupIRBuck
Features
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TM
HIGHLY INTEGRATED 9A
Description
The IR3821A
SupIRBuck
TM
is an easy-to-use,
fully integrated and highly efficient DC/DC
regulator. The onboard switching controller and
MOSFETs make the IR3821A a space-efficient
solution, providing accurate power delivery for
low output voltage applications.
The IR3821A operates from a single 4.5V to 14V
input supply and generates an output voltage
adjustable from 0.6V to 0.8*Vin at loads up to 9A.
A versatile regulator offering programmability of
startup time, power good threshold and current
limit, the IR3821A’s fixed 300kHz switching
frequency allows the use of small external
components.
The IR3821A also features important protection
functions, such as Pre-Bias startup, hiccup
current limit and thermal shutdown to provide the
required system level security in the event of fault
conditions.
WIDE-INPUT VOLTAGE, SYNCHRONOUS BUCK REGULATOR
Wide Input Voltage Range 2.5V to 21V
Wide Output Voltage Range 0.6V to 12V
Continuous 9A Load Capability
300kHz High Frequency Operation
Programmable Over-Current Protection
Programmable PGood Output
Hiccup Current Limit
Precision Reference Voltage (0.6V)
Programmable Soft-Start
Pre-Bias Start-up
Thermal Protection
Thermally Enhanced Package
Small Size 5mmx6mm QFN
Pb-Free (RoHS Compliant)
Applications
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Distributed Point-of-Loads
Server and Workstations
Embedded Systems
Storage Systems
DDR Applications
Graphics Cards
Game Consoles
Computing Peripheral Voltage Regulators
Fig. 1. Typical application diagram
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1
PD-60332
IR3821AMPbF
ABSOLUTE MAXIMUM RATINGS
(Voltages referenced to GND)
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V
IN
Supply Voltage
Vcc Supply Voltage
Vc Supply Voltage
SW
PGood
Fb,COMP,SS,Vsns
OCSet
AGnd to PGnd
Storage Temperature Range
Operating Junction Temperature Range
ESD Classification
Moisture Sensitivity Level
-0.3V to 24V
-0.3V to 16V
-0.3V to 30V
-0.3V to 30V
-0.3V to 16V
-0.3V to 3.5V
10mA
-0.3V to +0.3V
-65°C To 150°C
-40°C To 150°C
JEDEC, JESD22-A114
JEDEC Level 3 @ 260
o
C
Caution:
Stresses beyond those listed under “Absolute Maximum Rating” may cause permanent damage to the
device. These are stress ratings only and functional operation of the device at these or any other conditions beyond
those indicated in the operational sections of the specifications is not implied. Exposure to “Absolute Maximum
Rating” conditions for extended periods may affect device reliability.
PACKAGE INFORMATION
5mm x 6mm POWER QFN
12
V
IN
11
SW
10
PGnd
θ
JA
=
35
o
C / W
θ
J
-
PCB
=
2
o
C / W
HG
V
C
13
14
1
Vsns
15
AGnd
9
8
PGood
V
CC
2
3
4
5
6
7
FB COMP AGnd AGnd SS OCSet
Fig. 2: Package outline (Top view)
ORDERING INFORMATION
PACKAGE
DESIGNATOR
M
M
11/04/08
PACKAGE
DESCRIPTION
IR3821AMTRPbF
IR3821AMTR1PbF
PIN
COUNT
15
15
PARTS PER
REEL
4000
750
2
PD-60332
IR3821AMPbF
Block Diagram
Fig. 3. Simplified block diagram of the IR3821A.
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3
PD-60332
IR3821AMPbF
Pin Description
Pin Name
1
2
Vsns
Fb
Description
PGood sense pin. Use two external resistors to program the power
good threshold.
Inverting input to the error amplifier. This pin is connected directly to the
output of the regulator via resistor divider to set the output voltage and
provide feedback to the error amplifier.
Output of error amplifier.
Signal ground for internal reference and control circuitry.
Signal ground for internal reference and control circuitry.
Soft start / shutdown. This pin provides user programmable soft-start
function. Connect an external capacitor from this pin to signal ground
(AGnd) to set the start up time of the output voltage. The converter can
be shutdown by pulling this pin below 0.3V.
Current limit set point. A resistor from this pin to SW pin will set the
current limit threshold.
This pin provides biasing voltage for the internal blocks of the IC. It also
powers the low side driver. A minimum of 0.1uF, high frequency
capacitor must be connected from this pin to power ground (PGnd).
Power Good status pin. Output is open collector. Connect a pull up
resistor from this pin to Vcc.
Power Ground. This pin serves as a separated ground for the MOSFET
drivers and should be connected to the system’s power ground plane.
Switch node. This pin is connected to the output inductor
Input voltage connection pin
This pin is connected to the high side Mosfet gate. Connect a small
capacitor from this pin to switch node (SW).
This pin powers the high side driver and must be connected to a voltage
higher than input voltage. A minimum of 0.1uF high frequency capacitor
must be connected from this pin to the power ground (PGnd).
Signal ground for internal reference and control circuitry.
3
4
5
6
Comp
AGnd
AGnd
SS/SD
7
8
OCSet
V
CC
PGood
PGnd
SW
V
IN
HG
V
C
AGnd
9
10
11
12
13
14
15
Pins 4, 5 and 15 need to be connected together on system board.
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PD-60332
IR3821AMPbF
Recommended Operating Conditions
Symbol
V
in
V
cc
V
c
V
o
I
o
Note1
T
j
Definition
Input Voltage
Supply Voltage
Supply Voltage
Output Voltage
Output Current
Junction Temperature
Min
2.5
4.5
Vin + 5V
0.6
0
-40
Max
21
14
28
12
9
125
Units
V
A
C
o
Electrical Specifications
Unless otherwise specified, these specification apply over Vin=V
cc
=V
c
=12V, 0
o
C<T
j
(Ic)<105
o
C.
Typical values are specified at T
a
= 25
o
C.
Parameter
Power Loss
Power Loss
P
loss
Vcc=V
in
=12V, Vc=24V, V
o
=1.8V,
I
o
=9A, L=1.2uH,
Note3
2.3
W
Symbol
Test Condition
Min
TYP
MAX
Units
MOSFET R
ds(on)
Top Switch
Bottom Switch
R
ds(on)_Top
R
ds(on)_Bot
I
D
=11A, Tj(MOSFET)=25 C
I
D
=11A, Tj(MOSFET)=25 C
o
o
10.5
10.5
13.4
13.4
mΩ
Reference Voltage
Feedback Voltage
Accuracy
V
FB
0 C<Tj<105 C
-40
o
C<Tj<105
o
C,
Note2
o
o
0.6
-1.35
-1.5
+1.35
+1.5
V
%
%
Supply Current
V
CC
Supply Current (Static)
V
C
Supply Current
(Static)
V
CC
Supply Current
(Dynamic)
V
C
Supply Current
(Dynamic)
I
CC(Static)
I
C(Static)
I
CC(Dynamic)
I
C(Dynamic)
SS=0V, No Switching
SS=0V, No Switching
SS=3V, V
c
=24V, V
cc
=V
in
=12V.
V
o
=1.8V, Io=0A
SS=3V, V
c
=24V, V
cc
=V
in
=12V.
V
o
=1.8V, Io=0A
10
4.5
13
13
13
7
20
20
mA
Under Voltage Lockout
V
CC
-Start-Threshold
V
CC
-Stop-Threshold
V
CC
-Hysteresis
V
C
-Start-Threshold
V
C
-Stop-Threshold
V
C
-Hysteresis
V
C
_UVLO(R)
V
C
_UVLO(F)
V
CC
_UVLO(R)
V
CC
_UVLO(F)
Supply ramping up
Supply ramping down
Supply ramping up and down
Supply ramping up
Supply ramping down
Supply ramping up and down
4.0
3.7
0.15
3.1
2.85
0.15
0.2
0.25
4.4
4.1
0.3
3.5
3.25
0.25
V
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